In a countersuit filed Friday, Walter Kissinger, older brother of President Nixon’s secretary of state, claims Kevin and Elizabeth Cogan were supposed to take care of the Long Island manse where he lived with his late wife, Eugenie, but instead they left it in ruins, slept in the Kissingers’ bed while the owners were out of town — and even intentionally befouled the million-dollar home in a way too unseemly to print in a ­family newspaper.

Kissinger’s lawyers say the Cogans are in a ­financial bind and trying to sue their way out of it by exploiting their aging former employer.

The Cogans started working at the five-bedroom Huntington Bay mansion in 2007 with the understanding they could live rent-free in a guest cottage in return for taking care of the property. They are suing in Brooklyn federal court for back pay, overtime and damages.

But Kissinger claims they left the cottage and main house in such a mess, it dragged down the value of the chateau-style home. His countersuit — which demands that the Cogans pay damages to Kissinger — further claims that when the Kissinger family tried to sell the property in 2011, the Cogans refused to let potential buyers into the guesthouse so that nobody would discover the poor state in which it had allegedly been left.

The papers even claim that squirrels moved into the wrecked cottage and that the Cogans “took advantage of Mr. and Mrs. Kissinger’s advancing ages, and continued to accept the benefits provided to them while wilfully refusing to perform agreed-upon duties.” It also says they demanded $10,000 to move out of the cottage.

Lawyers for Kissinger called the Cogans’ suit “frivolous,” and alleged in the countersuit that “one month” before the Cogans’ suit was filed, a judge in a different case ordered Kevin to pay $146,396 to a homeowner he allegedly defrauded.